Collision-induced dissociation of MO+ and MO2+ (M = Ta and W): Metal oxide and dioxide cation bond energies

The collision-induced dissociation (CID) of TaO+, WO+, TaO2+, and WO2+ with Xe along with reactions of TaO+ and WO+ with O2 are studied as a function of kinetic energy using guided ion beam tandem mass spectrometry in order to elucidate the thermochemistry of the MO2+ species. The kinetic energy dependences for the CID reactions show endothermic behavior, whereas the MO++O2 → MO2+ + O reactions proceed near the collision limit indicating exothermic processes. Analyses of the endothermic CID reaction cross sections yield 0 K threshold energies in eV of E0(Ta+–O) = 7.01 ± 0.12, E0(W+–O) = 6.72 ± 0.10, E0(OTa+–O) = 6.08 ± 0.12, and E0(OW+–O) = 5.49 ± 0.09. The nature of the bonding in MO+ and MO2+ is discussed and compared for Ta and W and analyzed using theoretical calculations at the B3LYP/HW+/6-311 + G(3df) level of theory. Bond energies for all MO+ and MO2+ species are calculated using geometries calculated at this level as well as BHLYP and CCSD(T) levels and the Stuttgart–Dresden (SDD) and the Def2TZVPP basis sets. Reasonable agreement between the theoretical bond energies and experimental CID threshold energies for TaO+, WO+, TaO2+, and WO2+ is found. Potential energy surfaces for the reaction of the metal cations with O2 are also calculated at the B3LYP level of theory and reveal additional information about the reaction mechanisms.

Figure optionsDownload high-quality image (135 K)Download as PowerPoint slideHighlights
► In this study, we examine the collision-induced dissociation of tantalum and tungsten monoxides and dioxide cations.
► Reactions of tantalum and tungsten monoxide cations with molecular oxygen are studied.
► Bond energies for tantalum and tungsten monoxides and dioxide cations are determined and compared to theoretical and literature values.
► The dioxide cation thermochemistry determined here is much more precise that any previous determinations.